Optional additional CI for developer tools

I mostly work in VSCode and use the [Python plugin](https://github.com/microsoft/vscode-python) which has a debugger and test runner.

Occasionally something changes in distributed which breaks my development setup. For example right now the test runner is failing to discover tests and is reporting the error

```
____________ ERROR collecting distributed/comm/tests/test_comms.py _____________
distributed/utils.py:142: in _get_ip
sock.connect((host, port))
E OSError: [Errno 65] No route to host

During handling of the above exception, another exception occurred:
distributed/comm/tests/test_comms.py:48: in
EXTERNAL_IP6 = get_ipv6()
distributed/utils.py:173: in get_ipv6
return _get_ip(host, port, family=socket.AF_INET6)
cytoolz/functoolz.pyx:476: in cytoolz.functoolz._memoize.__call__
???
distributed/utils.py:151: in _get_ip
addr_info = socket.getaddrinfo(
../../../miniconda3/envs/dask/lib/python3.8/socket.py:918: in getaddrinfo
for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
E socket.gaierror: [Errno 8] nodename nor servname provided, or not known
```

I can work around this by setting the `DISABLE_IPV6` env var. Or by using `pdb` and `breakpoint` outside of the editor.

The same issue doesn't happen when running `pytest` from the terminal.

My initial reaction is to debug and fix the issue and add some CI to run the test discovery that is failing. But given that development tools boil down to personal preference (and installing them in CI can be arduous) perhaps we don't want some VSCode specific checks in our tests.

Does anyone have any thoughts or preferences about this?